This invention concerns improvements in the processing of video image signals to achieve so-called digital video effects.
In such processing, each field or frame of a television image is stored as a series of discrete digital values or pixels containing the luminance or chrominance information of the original signal and obtained by sampling the original signal at an appropriate pixel repetition rate. The original signal may be reproduced by scanning the store, or, by addressing the store in appropriately timed relation to synchronising signals defining the television raster, selected image information can be retrieved from the store and displayed on a television screen in any desired position or orientation. Such retrieved information may be combined with other image information to produce a pattern or collage of discrete images, and by moving the boundaries between respective patterns containing the separate picture information, various effects can be achieved.
One such effect is to give the illusion of several pictures moving in space, passing in front of and behind one another and/or intersecting. However, known devices for producing such effects suffer from unsatisfactory performance or one sort or another.